This is a Phase I clinical trial to assess the safety, pharmacokinetics, biodistribution and extent of tumor localization of a single dose of IV administered 131=I radiolabeled human anti-glioma MAb BT32/A6 in patients with a histologically confirmed malignant glioma (glioblastoma multiforme, anaplastic astrocytoma, gliosarcoma, anaplastic oligodendroglioma or mixed anaplastic glioma) with a measurable persistent or recurrent disease. Patients will receive a single IV infusion of approximately 1 mg of 131-I labeled MAb BT32/A6 (specific radioactivity = approximately 10 mCi/mg of antibody) per 70 kg IBW administered over a 30 minute interval. The objective is to obtain evaluable data for each of the 4 aforementioned parameters on a minimum of 6 patients. More than 6 patients may be treated to attain this objective, but the number treated will not exceed 20. The human MAb BT32/A6 is an IgM(k) isotype that recognizes a glioma cell surface antigen that is expressed in primary human gliomas and human glioma cell lines but not in normal human adult brain and other normal human adult tissues. A full pharmacokinetic analysis will be performed on all patients in this Phase I trial. Serum levels of 131-I MAb BT32/A6 will be quantified by a radiometric counting procedure. Analyses of the immunoreactivity of the radiolabeled MAb BT32/A6 in sera will be made. Serum samples will be assessed for immunoreactivity through a whole cell (SK-MG-1 malignant glioma) binding assay which compares relative % binding to control sera spiked with freshly labeled MAb BT32/A6. Pharmacokinetical parameters such as half-life, area under the curve (AUC), mean residence time (MRT), volume of distribution at steady state (VDss) and clearance rate (CL) will be estimated and compared using standard methods for pharmacokinetical analysis and modeling. Correlation and regression analysis will be conducted to examine the relationships among pharmacokinetical parameters, HAIA and toxicity. Dosimetry analysis will be performed to compare whole body dose and tumor to normal tissue ratios.